/*
#include<stdio.h>
main()
{

	int n,i;
	long int fac;
	printf("please input n (n>=0):");
	scanf("%d",&n);
	if(n>=0)
	{
		fac =1;
		if(n>0)
		{
			i=1;
			while(i<=n)
			{
				fac*=i;
				i=i+1;
			}
		} 
		printf("%d!=%ld\n",n,fac);
		
	}
	else 
	printf("error\n");
} 
*/
